Method for treating metals



' July 14,1936.

J. N. AK EN METHOD FOR TREATING METALS Filed June 18, 1930 5 n 1.11.|-H||J Tu a; TC D x a I INVENTOR ATTORNEYS wm Q NM m understood that theinvention is not to be limited.

Patented July 14, 1936 UNITED STATES PATENT OFFICE v 2,047,814 m-rrnonFon 'mna'rmc METALS James Nelson Aken, Rome, N. Y., assignor to GeneralCable Corporation, New York, N. Y., a corporation of New JerseyApplication June is, 1930, Serial No. 461,977

5 principal application in the tinning of copper wire. The invention wasdeveloped in this field and will be described with particular referenceto this application; but it is known that the invention has broaderaspects and uses so it is to be by reference to this particular field ofuse.

In order to illustrate the advance which the invention has made in theartit will be helpful to compare it withsome of the best of the prior 15practices.

In a typical present-day wire making plant the drawing of the wire isusually carried out in one departmentor room; the annealing of the wirein another department or room; and the g coating or tinning of the wirein still another department or room. The annealin of course, is madenecessary partially or wholly by the. diedrawing process which hardensthe wire.

After each of these processes the wire is left 25 wound upon spools and,sinceit is impossible or perhaps impracticable'to carry the wiredirectly from one process to the next, there is necessarily aconsiderable. amount of inter-process storage. It is preferable to havestorage immediately after 30 the drawing process while the wire is hardrather than after the annealing process while'the wire is soft becausethe hard wiredoes not oxidize nearly so badly as the soft annealed wire.It is one of the objects of the present invention to avoid 35 entirelythe storage of soft annealed wire.

According to the present practice annealing is carried out in a gasheated nuflie, the wire (or at least copper and other'no'n-ferrous wire)passing through water baths before and after enter- 40 ing the heatingmuiiie. Thewater entering the mufile with -the wire from the first bathmust be evaporated during the annealing heating. This entails heatlosses. Further; the annealing heat is lost for any succeeding processfor the wire 45 becomes completely cold. after the annealin 35 tion.

50 heat losses.

process. In addition the heat useful for annealing the wire has to passthrough the thick muflle walls and through air or other gases which arepoor conductors of heat. This entails further Moreover, this method ofheating to anneal seems to bake onto the wire any oil or dirt which mayand usually does remain from the drawing process in a manner whichseriously hinders subsequent cleaning and tinning opera- The wateradhering to the wire from the last bath enhances oxidation while thewire is in storage.

Heretofore, the wire preparatory to tinning has been cleaned in an acidbath. This treatment eats away a certain amount of the wire; requiresspecial and expensive castings; gives off dangerous fumes which cannotbe turned into the air but must be especially treated and diluted topass off into the sewerage, this'again requiring expensive castings andother accessories; gets the metal intothe tin bath to cause trouble;furnishes the wire in a cold state to the tin bath; and has "other evilfeatures. The present invention aims to eliminate these evils.

Coming to the coating ortinning treatment is the fact that wire from theacid bath comes to the coating apparatus in a cold state requires a longbathof hot molten tin (or such other metal as may be used for coating)to bring the wire to heat. This gives time for the hot 'tin to attackthe surface of the wire to cause dilution of the tin bath. Tests of suchbaths show the tin to be reduced to 98% or even as-low as 94% purity.Below thatit cannot beused. The necessary large bath of heated tin alsohas heavy vapor losses. The present invention aims to avoid theseobjectionable features; keep the tin bath in a substantially pure state;and provide certain additional benefits and advantages which could notbe realized before.

Other objects and advantages of the invention will be apparent from thefollowing description of a preferred form of the invention. The singlefigure of drawing is a diagram to assist the description.

,According to the preferred form of the new invention as well as inthepast practice the wire is taken from the drawing dies Ill by aconstant speed capstan II and wound upon spools l2. These spools aresubject to certain delay or storage before the next treatment. Thisstorage point is designated byv the numeral l5. Thewire here is hard andwill not readily oxidize. I

'Wire from storage point l5 may be used for various purposes. Perhapsonly a relatively small part will be coated but it is this part whichcon-. cems the present invention.

Previously, as shown in broken lines, the wire was transported to anannealing oven l6 sealed at, each end with water baths l1 and I8, woundagain upon spools (unless run through the oven on the spools) and placedin soft wire storage at point 20. From the point the wire wastransported to the tinning apparatus and passed sucbath 22. Finally thewire passed through a series of wipers 23, a water cooling bath 24 andwas wound upon spools. Thereafter the spools were transported to storageat the point 25.

In the new process shown in the diagram by full lines, the wire incommon with the old process is taken from the storage point l and isfinally delivered to the storage point 25 but between these points ittravels a different route. The annealing and conditioning for thetinning treatment are both accomplished in one and the same treatment bypassing the wire through a hot liquid bath 30. This may be an oil bathat a temperature of about 500 F., this having been found suitable forthe grades and sizes of wire which have been processed to date. Corn oilhas proved most satisfactory because it does not vaporize readily orcreate a fire hazard at the temperatures to be maintained. It alsofulfills the major requirements of the process in a highly satisfactorymanner. These requirements are: to anneal the wire, to give a light buteffective film over the wire to prevent oxidation, and to act as a fluxfor the succeeding tinning treatment. In varying degrees other oils suchas mineral oil, palm oil, peanut oil, etc. and even ,non-oleoussubstances such as molten salts, soaps, etc. have proved successful. I,

The flux-anneal bath may be heated in any desired manner. It lendsitself very well to the use of an immersed electrical heating unit 3|which has various advantages such as avoiding conduction losses throughthe walls of the vessel containing the bath. With such an arrangementthe whole unit may be thermally insulated as indicated by double linesin the drawing. Means of any suitable kind are provided for condensingthe vapor from the bath so the liquid thus obtained may be re-used.

The wire. from the annealing bath passes directly to the tin bath 32 soas to conserve the heat imparted to the wire by the annealing bath,though it is not necessary to keep the wire from the air since itcarries a protective film of the annealing liquid. Thus annealing andmining are made one continuous process requiring no intermediate softwire storage.

Since the wire remains hot until it enters the tin bath the latter maybe made very short. A

bath of about 20% of the present bath capacity is adequate. The tin bathmay be at about 450 1". so even with a slight cooling after leaving theannealing bath the wire enters at about the same temperature as the tinbath. A short bath does not give -the wire time to go into solution inthe tin. Also the bath is rapidly used up and renewed. Both of thesefactors aid in maintaining the bath in a high state of purity.

It is to be noted that the supply spools of wire are disposed within theannealing bath thus permitting the wire to heat before it is unreeled.For each take-oil spindle there are in the bath 30 two spools of wire,spool A annealing while spool B is being run 011' and vice versa. Forannealing #30 copper wire it should be in the bath at 500' 1". aboutfive minutes. Then, no matter what drawing speed through the tin bathmay be want- .ed the annealing treatment will not prevent itsrealization. A speed of 600 ft. per minute hasbeen found to give goodresults for #30 wire. A wipe 23 is used for the wire leaving theannealing .bath while a wipe 34 is used for the wire leaving the tinbath. Thereafter the wire may be passed through a coolingbath 35provided with wipe it. If the spindles for the spools on which the wireis reeled from the tinning bath run at constant speed the wire will bepulled through the bath at varying speed which increases as the spoolsfill up. This causes a part of the wire, when the spool first starts tofill up, to be overtinned on account of its slow speed through the bathwhile when the spool is almost completely filled the wire isunder-tinned due to its increased speed through the bath. According tothe present process a uniform coating is put on the wire throughout itsentire length. This is provided by drawing the wire through the bath atconstant lineal speed.

Herein capstans 31 have several turns of the 0 wire placed around themand are run at a constant speed to deliver the wire to spools 38. Thespools 38 are driven in resilient fashion as by friction drive means totake up the wire as fast as it is delivered from the capstans.

It is found that the wire is cleaner when produced by the presentprocess due to the fact that it has not oxidized as much as it did withprevious methods and of course dirt and oil from the drawing processhave not been burned into thewire as they were in the dry annealingprocess. The hot oil used in the present methodacts to remove the oiland refuse left on thewire by the drawing process.

Also it is noted that a thinner and more even coating of tin is presentwhen the wire reaches the wipe than with previous processes. There isvery little excess tin on the wire at this point. Whereas two wipeswere. previously necessary, satisfactory wire can now be produced withone wipe, and even then very little tin is collected at this wipe.

There is a great saving .in time by the new process due to the fact thatthere is no storage of wire as previously between the annealing andtinning. treatments. Considerable saving in floor space is also realizedbecause of the fact that one storing is omitted: because one treatingde- .vice is omitted; and because the treating devices which areretained are much smaller than previously. Further, a great deal oflabor is saved by omitting operations and avoiding unnecessary handlingbetween operations. Mention has already been made of the saving in heat.Tin is also saved because the oil appears to form a film on the surfacethereof to reduce dross. Tests carried out according to the method ofthe American Society of Testing Materials, Specification B 3321"Standard Specifications for Tinned Soft or Annealed Copper Wire forRubber Insulation" have shown that the coating applied according to thepresent process is superior to coatings previously applied. Of sevensamples of wire tinned according to the present process and sevensamples of wire tinned accordingto the generally acknowledged as bestprevious commercial process the following comparative results wereobtained:

Previous:

3 samples failed at 5 cycl 2 samples failed at 6 cycles. 1 sample failedat 8 cycles. 1 sample failed at 11 cycles.

Present:

2 samples failed at 9 cycles. 2 samples failed at 13 cycles. 3 samplesfailed at 14 cycles.

In addition to the above advantages the cost of acid is saved and thedanger of operators being bumed by acid or injured by acid fumes isavoided. The 011 or other fluid used is an added acme cost but is muchless than the saving eflected on the acid alone.

While one embodiment of the invention has been described for purposes ofillustration it'is to be understood that the invention is not thuslimited but may be variously embodied within the scope of subjoinedclaims.

What I claim is:

-1. The method of treating unannealed copper wire which comprises,storing spools or packages of the wire in hot corn oil until theannealing temperature is reached, unreeling the wire from such spoolswhile alternate spools of wire are annealing, passing the wire as itunreels from the oil bath and before it cools, into a hot tin bath,wiping the wire to remove excess tin, passing the wire through a coolingbath and a drying wipe, and winding the wire at constant lineal speedupon spools. Y

2. The method of treating unannealed cuprous wire which comprises,subjecting the same toan annealing-fluxing bath of hot corn oil whichremoves adherent substances irom the previous diedrawing process, formsa protective film there.- over and anneals the wire, and subsequentlywhile the wire is hot subjecting it to a tinning bath in 'a separatevessel for the purposes set forth.

3. The method oi treating cold-worked. cu-

-prous wire which comprises subjecting the wire to a hotfluxing-annealing bath of oleaginous material for a period long enoughand at a temperature high enough to flux and anneal the wire. removingthe wire from the fluxing-annealing bath, and subjecting the wire to abath of molten metal to form a metal coating thereon.

4. The. method set forth in claim 3 in which the cuprous wire is passedbefore cooling from the annealing oil bath through the metal-coatingbath.

5. The method set forth in claim 8 in which the annealing oil bathis ina separate vessel and is of a higher temperature than the metal-coatingbath and in which the cuprous wire passes from the annealing bath to thecoating bath so as to reach the latterat approximately the temperaturethereof.

6. The method of treating cuprous wire which 20 comprises subjecting thewire to a hot bath of oleaginous material for a period long enough andat a temperatme high enough to effect an annealingdluxing treatment at asingle stage, and subsequently tinning the-annealed wire,

JAMB- NELSON Am.

